Overhead loader



May 10, 1960 Filed Nov. 5. 1957 P. R. PUESCHNER ET AL OVERHEAD LOADER 6 Sheets-Sileet 1 nu: L4-

INVENTORS PHIL/P R. PUESCHNE'R GERALD R LAME/E ATTORNEYS May 10, 1960 P. R. PUESCHNER ET AL OVERHEAD LOADER 6 Sheets-Sheet 2 Filed Nov. 5, 1957 INVENTORS PUESCHNER PHIL/P R. GERALD R LAME/2 ATTORNEYS May 10, 1960 P. R. PUESCHNER ET AL 2,936,036

OVERHEAD LOADER Filed Nov. 5, 1957 6 Sheets-Sheet 3 I f DINVENTORS PHIL/P R. PT/Z'SEI'NER GERALD R LAME/2 ATTORNEYS y 1960 P. R. PUESCHNER ETAL 2,936,086

OVERHEAD LOADER 6 Sheets-Sheet 4 Filed Nov. 5, 1957 IN VENTORS Pfl/L/P R. PUESCHNER. GERALD E LAME/2 ATTORNEYS y 10, 1960 P. R. PUESCHNER ET AL 2,936,086

OVERHEAD LOADER 6 Sheets-Sheet 5 Filed Nov. 5, 1957 :E-EI I -Ill IN VENTORS PHIL/P R. PUESCHNER GERALD F. LAME/2 ATTORNEYS I y 1960 P. R. PUESCHNER ET AL 2,936,086

OVERHEAD LOADER Filed Nov. 5, 1957 6 Sheets-Sheet 6 INVENTORS PH/L/P R. PUESCHNER GERALD R LAMER ATTORNEXG 2,936,086 OVERHEAD LOADER Philip R. 'Pueschner, Wausau, and Gerald P.'Lam'er,

. 'Schofield, Wis.,- assignors to Drott Manufacturing Corporation, Milwaukee, Wis., a corporation of Wisconsin Application November 5, 1957, Serial No. 694,582 18. Claims. .(Cl. 214-140 This invention relates to overhead'lo ade'rsif An'object' of this invention is to improve thefmeans' for rotating the main-lift arms of an overhead loader from a load receiving position to'a load dumping position. An-

other object of 'the invention is to provide meansfor protecting an operator of an overhead loader against accidental'dumpingwhile 'the load is overhis head.

These and other objects of the invention 'will be more readily apparent from the following description.

Overhead lift In overhead loaders constructed in accordance with thep'rior art, the main lift arms 'are ordinarlypivoted by means of a hydraulic jack. This hasp'resented a 'very serious pfoblem in that-with theordinary mountings of "thehydraulic jack, it can only rotate a pivotally mounted *arm'through an angle of less than 180. Even'then, at

the end of its stroke, 'the jack is approximately parallel to the arm it is supposed todrive so that practically'all leverage is lost.

Prior attempts to overcome this problem include com 'plicated multiple linkages and-special cam systems for shifting the pivotal connection of the'jack withthe driven "member as the jack advances it. -However, such prior art constructions have been generally unsatisfactory be cause of their complexity.

.Simplicity is combined with-efliciency in the structure of this invention by the novel mounting of the hydraulic jack. Instead of mounting the jack at some point'along the effective length of the cylinder in accordance with prior art practices, the mountingofthe cylinder is placed ahead of the retractedposition of theram. This is accomplished 'by the provision of a cylinder extension.

*Oneadvantage of this is that on the first part'of the driving stroke of the hydraulic jack the driven member is moving from a position in back of the effective position -(the pivot aifordedby the cylinder extension) of *sides of the "mounting of the cylinder, thetheoretical operative range of pivotal movement to be imparted to a lift arm is'doubled. Thus, lift arms may be nowrotated throughangles in excess of 180 Without serious loss of leverage by asimple single hydraulicjack.

The improved liftarm rotating means may be'g'ener'ally described as'comprising a frame pivotally mounting a lift'arm, a hydraulic cylinder having an extension yoke I at-its forward'endpivotally mounting it on the frame, a

piston in thecylinder. and a piston rod having its forward -end pivotally connected'with'the lift arm.

:1 Obviously these "advantages of. this invention "are j also applicable to any mechanical combinationwhere a pivnited' States. Patent its cylinderextehsionpivot and'thereby maintain a gen- 2,936,985 Patented May 10, 1960 otally'mounted arm is to be rotated through a wide angle approaching'or' exceeding 180.

An important element of thisst'ruc'ture isithe cylinder extension yoke which places the 'pivot of the cylinder on the frame ahead'of the pivotal mounting of the piston rodon the lift arm at the time when the hydraulic jack is retracted.

In operation, the'piston rod pivot passes from one side of the cylinder pivot to the opposite side as the jack isexten'ded for lifting. This arrangement of filements'causes the hydraulic jack to rotate rapidly on family tangential position with respect to the arc through which the lift arm is rotated.

' The relative positions of the pivotal connections of frame, arm and jack are important. The pivotal mounting of the lift arm on'the frame must be equidistant from the pivotal connections of the piston rod and cylinder extension with the lift arm and frame respectively.

Preferably, the pivotal mounting of the cylinder ex- .tension should be so mounted with respect to the pivotal mounting of the lift arm that maximum leverage may be applied to the main lift arms when the load is in the position demanding the greatest lifting force.

in one preferred form of the invention, this is accomplished by placing each cylinder extension forward and slightly above the level of the mounting of each main lift arm pivot. In a modified form of the invention, the

.same result is accomplished by placing the cylinder extension .pivot below and slightly to the rear of the pivot of-the main lift arms. -In the modified form, each main lift arm is formed as a bell crank acting about its pivot.

To obtain the advantage of the lifting arrangement of this invention requires the pivotal connections of the piston rod and arm to pass through a point of dead alignment with the pivotal connection of the cylinder extension and frame. This would appear to. present a serious problem in that the instant the two pivots become aligned,

:thepiston andcylinder are free to swing by momentum,

gravity or any other force into a position of non-alignmentwhich will lock the unit and render the hydraulic jack useless. That problem is solved in thisinvention by means of a cam track on each lift arm for operative engagement by a cam follower mounted on an elongated portion of the cylinder extension. Thus the cam means keep the hydraulic jackiproperly aligned with respect to the lift arm during the critical period of movement.

'Obviously other arrangements of cams and equivalent structures may be used so long as proper angular alignment of the hydraulic jack is maintained during the time its two pivotal mountings are in axial alignment.

Overhead dump prevention 7 In 'fthis and other types of overhead loaders, thereis the constant danger that the operator may accidentally dump the load while it is directly overhead. In accordance with this invention, this danger is completely avoided in all overhead loaders wherein a hydraulic jack for dumping the bucket is mounted to pivot about a connection with the tractor or frame asthe load is carried from receiving to dumping positions. This is accomplished by a swivel connection for the dumping hydraulic jack, including ring grooves within the swivel for feeding hydraulic fluid to the jacks and means for blocking the ring groovepassages While the bucket isv overhead. The blocking means may be merely filled portions of the grooves for engagingthe hydraulic fluid feed ports when fthe'r'otational position of the lift arms is such that the This effectively deactivates the v bucket is overhead. dumping mechanism temporarily.

The invention will bev better understoodby reference 7 to the attached drawings in which:

"Fig. 1 is a side elevational view illustrating a preferred form of the invention with the bucket in digging position;

Figs. 2-7 are additional side elevational views of that form of the invention illustrated in Fig. 1;

Fig. 2 shows the bucket elevated to carry position;

Fig. 3 shows the bucket at a level for front dumping;

Fig. 4 shows the bucket dumped forwardly of the tractor;

Fig. 5 shows the bucket in the no-dump position;

Fig. 6 shows the bucket in position for rear dumping;

Fig. 7' shows the bucket dumped rearwardly of the tractor;

Fig. 8 is an exploded perspective view diagrammatically illustrating the mounting of the lift arms and the dumping mechanism on the two Webs of the frame at each side of the tractor;

Fig. 9 is a diagrammatic plan view further illustrating the relative positions of the same elements;

Fig. 10 is an end elevation, partially in section, showing the detailed construction of one of the jacks for operating the lift arms;

'Fig. 11 is a sectional view taken along lines 11-11 of Fig. 10;

Fig. 12 is a broken sectional view, partially in elevation, showing the extensible link for leveling and dumping the bucket together with the mounting therefor whichforms the overhead dump prevention feature of the invention;

Fig. 13 is an end elevation showing the swivel pin of the mounting for the jack illustrated in Fig. 12;

Fig. 14 is a sectional view of the swivel illustrated in Fig. 12 and taken along lines 14-14 of Figs. 16 and 17;

Fig. 15 is another sectional view of the same swivel bushing taken along lines 15-15 of Figs. 16 and 17;

Fig. 16 is another sectional view of the same bushing taken along lines 16-16 of Figs. 14 and 15;

Fig. 17 is a sectional view of the same swivel bushing taken along lines 17-17 of Figs. 14 and 15;

Fig. 18 is a detailed view further illustrating the relative positions of the pivotal mountings of one lift arm and the jack driving it;

Fig. 19 is a side elevational view illustrating a modified form of overhead lift; and

Fig. 20 is an enlargement of a portion of Fig. 19, further illustrating the relationship of one lift arm and the hydraulic jack driving it.

Referring now to Fig. 1, a crawler tractor indicated generally at 10, including the usual motor, tracks, seat and operating controls, not specifically illustrated, is provided with a frame 12 firmly mounted on each side of the tractor to form a support unit for the loading attachments.

A pair of lift arms 14 are pivotally mounted on frame 12 at pivots 16, one being on each side of the tractor for movement as a unit. A connecting bar 18 (Figs. 8 and 9) extends between arms 14 to form the arms into a bucket carrying yoke. A bucket 15 or other load carrying means is pivotally mounted on the outer ends of the lift arms 14. The lift arm pivots 16 are generally centered with respect to the tractor to afford substantially equal unloading reach, both forwardly and'rearwardly.

Each arm 14 is powered by a separate double-acting hydraulic jack 20, operated by a conventional common control, not shown, to assure simultaneous co-ordinated action of the arms. 'Inasmuch as the lift jack mounting at each side of the tractor is the mirror image of the other, only one will be described in detail.

The jack generally identified at 20 in Figs. 1-7 is shown in detail in Figs. 10 and 11. It includes a cylinder 22, a ram 32, and a yoke in the form of a pair of cylinder extensions 24 and 26 provided with bushings 28 and 30 respectively for pivotally mounting the cylinder separate extensions on separate webs of frame 12.

The ram 32 includes a piston 34, a piston rod 36 and a swivel connection 38 for pivotally attaching the ram to lift arm 14. In the retracted positions of Figs. 10 and 11, the ram pivot 38 is back of the cylinder pivots at 28 and 30. As the ram 32 is extended, the axis of pivot 38 passes through direct alignment with the axis of pivots 28 and 30.

To avoid the possibility of jack rotation about the common axis of ram and cylinder at the moment of alignment, cylinder extension 26 is provided with an elongated portion 40, which is actually a cam follower arm provided with a cam follower in the form of roller 42.

Follower 42 rides in cam track 44 (Fig. 8), provided on arm .14. Track 44 is curved to follow the arc of roller 42 as the jack 20 pivots to generally tangentially follow the arc subscribed by lift arm 14.

Thus in the lift operation the bucket 15 may be moved from the position shown in Fig. 1 to the position shown in Fig. 7 through an arc of almost 180 while maintaining good leverage. Less than maximum leverage is obtained in movement from the position of Fig. 1, but maximum leverage is obtained at about the position shown in Fig. 2 where the load is the greatest distance away from the tractor. From there, leverage decreases as movement progresses, as can be obtained by inspection of the drawings in Figs. 1-7 showing the various angles of the jack 20 with respect to varying positions of lift arms 14.

In that form of the invention illustrated, the bucket 15 is self-leveling by reason of a parallelogram linkage at each side of the tractor. Each such linkage includes a link 50 having one end pivotally mounted on the bucket 15 and the other end pivotally connected with an intermediate link 52.

Intermediate link 52 is pivotally mounted intermediate its ends on lift arm 14. An extensible link in the form of a hydraulic jack 54 is pivotally mounted at its cylinder end on frame 12 by means of a side bracket not shown. The ram end of jack 54 is pivotally connected with the other end of intermediate link 52. Extensible link (hydraulic jack) 54 forms the dumping mechanism for the bucket in either its forward or rearward positions as indicated in Figs. 4 and 7.

Overhead dumping is prevented by the mechanism illustrated in Figs. 13-17. Jack 54 includes the usual piston 60, rod 62 and cylinder 64. Hydraulic fluid is fed to each jack 54 from a common conventional control system through hoses not illustrated, and thence through the swivel connector indicated generally at 69 mounting the jack 54 on the frames 12 by means of bracket 13 (Fig. 8). The swivel connector 69 includes a swivel pin 70 (Figs. 12 and 13) and a swivel bushing 71 (Figs. 12, 1417). The pin 70 is provided with hydraulic fluid passages 72 and 74 having ports 73 and 75 for the extension and retraction sides, respectively, of piston 60.

The bushing 71 is provided with packed sealing grooves 79, and 81 and hydraulic fluid passage grooves 82' and 84 in communication with ports 73 and 75 forming the ends of passages 72 and 74, respectively. Groove 82 has a port 92 in direct communication with the extension end of cylinder 64 by way of passage 93. Groove 84 is similarly provided with a port leading to the retraction end of cylinder 64 by a conduit not illustrated.

As can best be seen in Figs. 14 and 15, groove 82 is partially filledat 83. Figs. 16 and 17 show that groove 84 is also partially filled'at 85. It will also be noted that filled portions 83 and are spaced apart to correspond with the 90 spacing of the swivel pin ports of passages 72 and 74, so that as pin 70 and bushing 71 are rotated relative one to the other, hydraulic fluid passages 72 and 74 are in direct communication with jack 54, except for that part of the pivotal movement where filled portions 83 and 85 of grooves 82 and 84 block ports 73 and 75.

In mounting this swivel connection on'the tractor, the relative position of pin 70 and bushing 71 is such that filled portions 83 and 85 only block ports 73 and 75 during; the; time. that: lift: arms+1-4 move fromqthe: position shown in Fig; 3: tothe:positionshowncinrFigo; Irltth position: shown? ina Fig. 5 an operator:- would: be: unable to dump the bucket. Any; manipulation ofsthe controlsat that.-time:would-merely place:astrainzon the hydraulic lines. without extending. or retracting: jack:.54.

The novel structure of the invention has heen described without: reference. to conventionaldetails such.- as' pivotal connections, hydraulic controls, hydraulic: hoses-,"piston' rings and the like, 'as. these matters will bev understood byth'ose skilled. in the art;

Important detailed relationshipsiof theelements of the invention will be more. clearly: understood; however, byl reference to Figs. 8, 9 and 18 of the invention- Frame 11 is! formed. of two vertically. disposed webs 12(a): and 12(12)- for: mounting the entire: lift assembly. 'Pivot' 16 of arm 14 includes: a pin, not showngpassing through a pair of holes 17' in each web:12(a) and. 12(1)), only one hole being illustrated in Fig;- 8; The cylinder extensions 24 and 26 are mounted: on: webs 12(a) and 12(5), respectively, by means: ofpins25' and 2.1 (Fig. 9:), respectively, extending through extension holes 29' and 31 and web holes 33 and 35 (Fig.8), respectively. Referring nowto Fig. 18, it will be clear that the axis of pivots 38 and. 30 are equidistant from the axis of pivot- 16. This avoids locking the liftassembly asjack 20' pushes pivot 38 from a point below thezlevel of.

pivot 30 (as in-Fig. 1) to a'point above it asin Figs: Sand 18.

In operation inaccordance with thei-present' invention,

control system, an operator will retract jack 20 to lower the bucket 15 to-the digging position shown in Fig.- 1'; Thetractor or other vehicle-will then advance to fill the bucket. 15, and jack 54-will' be slightly extended to roll the bucket 15 back to the carrying position. Thereafter, the load maybe lifted to the carry position of Fig. 2 and transported to a suitable-'placefor dumping. If the load is to be dumped forwardly ofthe tractor, the arms 14 are placed in the position shown in Fig. 3 and dumping is accomplished by retracting jack 54 as illustrated in Fig.4. If the tractor is to be used for rear-end dtunping to take full advantage of the overhead feature, the lift arms will be swung directly from theposition illustrated in Fig. l'to the position illustrated in Fig; 6, where dumping will be accomplishedby extending jack 54, as illustrated in Fig. 7. The mounting-of lift jacks 20* give them good leverage on arms 14 'throu'ghout. A's pivot 38 approaches axial alignmentwi-th' pivot 30', Fig. 2, each cam follower roll 42'enters it cam track 44' to maintain angular alignment of jacks 20' with respect to arms 14- during the moment of' 'actual axial alignmenti Prior tothe-moment of alignment, the jack 20 is moving towards 'a' point of leverage but continued rn'ovementpast that point reduces the leverage of each jack 2%) on its respective arm 14. a

In the modification shown in Figs. 19 and 20, a tractor 110, provided with frames 112, mounts an overhead lift' mechanism operative in accordance with this invention. Mounted on the frame 112 at pivot'point116 are a pair of lift'arms 114, only one being shown.

A bucket 115 is pivotally'mounted on'the outer ends of the lift arms and its relative pivotal position is determined by the linkage elements. 150,152 and 154 as in Y 'tion therewith, said ram-lifter pivot being on .oneisidez the other illustrated forms of the invention.

A hydraulic jack 120, provided with a cylinder extensionzl24, is pivotally mounted at 130 on each side? of it will be seen that'through a conventional hydraulic the traictonon the frame 112 In thisform of the invention, each lift arm is shaped to include a rearwardly ex-' tending bell crank arm 1 99. v

The piston 136 of jack is pivotally connected to arm 199 at a point not discernable in Fig. 19 because it is in direct alignment with the cylinder extension mounting in the position illustrated.

A cam track 144 on arm 199 in co-operative relation ship with cam follower=142 on extension 124 holdsthe jack. 120411 proper drivin'grelationship despite the axial alignment of the piston and cylinder'pivot mountings".

It will be clear that this structural modification does not alter the basic operatingrelationship of the invention.

By reason of the filled or blocked portions 83 and85 in'the grooves of bushing 71, dumping cannot be accomplished when the lift arms 14 are in the position illustrated. in Fig. 5. In that position, portions 83 and85 completely block ports73 and 75 to inactivatethe jack 54 temporarily.

What is claimed is:

1. An overhead loadercomprising a self-propelled vehicle, a frame mounted. at each side of the vehicle, a pair of load carrying arms, one being pivotally'mounted on the frame at each side ofthe vehicle,,a load-carrying receptacle mounted at the outer end of said arms and a hydraulic. jack for each. of said arms, each said hydraulic jack including a ram pivotally connected to one of said arms and a cylinder with a cylinder extension, a cylinder extension pivot mounting said cylinder on said frame in a position ahead of the pivotal mounting for said. ram when said ram is fully retracted, the end of said.cylinder-opposite'said extension being rotatable about said cylinder extension pivot during extension and retraction of the jack;

2. Means for. rotating a pivotally. mounted arm through a wide angle while maintaining leverage comprising abase supporting said arm, a hydraulic cylinder pivotally mounted on said base by means of an extension as the sole mounting therefor, a pistonin said cylinder andra piston rod extending outwardly from said cylinder in the same direction as said extension and pivotally; mounted at'its outer end to said arm, the pivotal mountings of said cylinder extension on the base and'said piston rod on the arm being equidistant from'the pivotal mounting of said arm on the base whereby said pivotalmountings will be axially aligned in one intermediate positionv of piston extension and the pivotal mounting of said piston rod being on one side of said cylinderextension pivot'in the retracted position on the opposite side in the extended position. 7

3. Means as set forth in claim 2 including, in addi-- tion, means for maintaining angular alignment of said piston and cylinder with respect to said arm as their.

pivotal connections reach and pass the point of axial' vehicle provided with a mounting frame, a buclnetlifter pivotally mounted on said frame, a bucket mounted'at the outer end of said lifter and a hydraulic jack for: pivoting said lifter from a loading position at one end of the vehicle to an unloading position at the opposite end of'the vehicle, said jack comprising a ram having a. single pivotal connection with said lifter,. a cylinder and aram-end cylinder extension having a single pivotal connection with said frame as the sole cylinder connec-J of the extension-frame pivot When the'bucket is lowered' for loading and on the opposite side when the bucket 7 of the ram-lifter pivot and the axis of the cylinder extension-frame pivot are equidistant from the axis of the lifter-frame pivot.

8. A loader as set forth in claim 7 wherein cam means operative between said lifter and said cylinder extension are provided for maintaining angular alignment of said jack with respect to said lifter when the ram and cylinder pivots come into axial alignment.

9. A loader as set forth in claim 8 wherein the pivotal mounting of said cylinder extension on said frame is forward of the pivotal connection of the lifter on said frame to provide maximum leverage at the position where the load is farthest from the vehicle.

10. A loader as set forth in claim 8 wherein the pivotal mounting of said cylinder extension on said frame is spaced from the pivotal connection of the lifter on said frame in'a relationship placing the axis of the cylinder extension-frame pivot and the axis of the lifter-frame pivot in alignment when the lifter load is in the position of greatest mechanical advantage with respect to said vehicle.

11. An overhead dump preventor for an overhead loader wherein lift arms pivotally mounted on a vehicle swing a bucket at their outer ends from one end of the vehicle to the opposite end and a hydraulic jack is employed to dump the bucket, comprising hydraulic fluid feed lines for said jack passing through a swivel mounting for said jack, said swivel being responsive to the rotational position of said lift arms, said swivel including a relatively rotatable swivel pin member and swivel bushing member, one of said members being provided with hydraulic fluid inlet passageways and the other of said members being provided with hydraulic fluid outlet passageways, and said members forming one with the other a ring groove placing said inlet and outlet passageways in communication, and a solid portion on one of said members effectively filling said groove and blocking one of said passageways when the lift arms are overhead.

12. An overhead loader comprising a vehicle, a lift arm assembly rotatable from aground engaging position at one end of the vehicle to a dumping position at the other end of the vehicle, load carrying means pivotally mounted at the outer ends of said arms and a linkage means including a hydraulic jack for dumping said load carrying means by pivotal movement at the end of said arms, at least one fluid passage for said jack and means responsive to the angular position of said lift arms for closing said passage when said load carrying means are overhead.

13. In an overhead loader wherein lift arms pivotally mounted on a vehicle swing a bucket at their outer ends from one end of the vehicle to the opposite end and a hydraulic jack dumps the bucket, that improvement which comprises routing the hydraulic fluid for said jack through a swivel, the rotational position of which is res'ponsive to the pivotal position of said lift arms, said swivel including a swivel pin member and a swivel bushing member, one of said members being provided with a fluid inlet port in communication with a source of hydraulic fluid, and the other of said members being provided with a fluid outlet port in communication with said jack, and said members forming one with the other a ring groove placing said inlet and outlet ports in communication, and one of said members being provided witha filler block closing a portion of said groove in all positions of said swivel and closing one of said ports when said swivel is turned to a position indicating an overhead position of said arms.

carried'overhead loaders, which are dumpable by a hydraulic jack, comprising a swivel, the rotational positions of which are responsive to'the positions of the load, with respect to the vehicle, and hydraulic fluid feed means for-said jack including an outlet passage leading from said swivel to said jack and an inlet passage leading from a source of hydraulic fluid to said swivel, said swivel being provided with fluid passage means placing said inlet and outlet passages in communication with one another, and means for closing said fluid passage means within said swivel at predetermined rotational positions thereof corresponding to the positions in which the load is overhead with respect to an operator on the vehicle.

15. An'overhead loader provided with overhead dump prevention means comprising a self-propelled vehicle, frame members at each side of the vehicle, a pair of lift arms, one pivotally mounted on each of said frames, a bucket pivotally mounted on the outer ends of said arms, means for rotatingsaid lift arms about an angle of about for loading and unloading positions at opposite ends of the vehicle, parallelogram linkage means for continuously leveling said bucket throughout the operational movement of said lift arms, said linkage means including a hydraulic jack having its cylinder pivotally mounted on said frame and the pivotal mounting for said jack including a nonrotatable swivel pin and a rotatable swivel bushing, a pair of hydraulic lines leading from a source of hydraulic fluid to said swivel pin, a pair of hydraulic fluid passages leading through said pin to axially spaced ports for each, a pair of partially filled ring grooves in said swivel bushing forming with said swivel pin a pair of hydraulic fluid passages, one communicating with each of said ports, and a port in each of said ring grooves leading to opposite ends of said hydraulic jack, the relative rotational position of said pin and bushing being such that said grooves are in direct communication with said pin ports at all times except when the lift arms are directly overhead and the partially filled portion of said grooves block said pin ports when the left arms are overhead to prevent actuation of said jack and thereby to prevent overhead dumping.

16. A hydraulic jack comprising a ram and a cylinder provided with a yoke extending forwardly thereof to form a single pivotal mounting therefor, said single pivotal mounting being the sole cylinder mount.

17. Aswing motion for a pivoted member comprising an extensible member having a driving pivotal mounting and a driven pivotal mounting and means for driving said driven mounting, said driving mounting being spaced from said driving means and in a position alternately on opposite sides of said driving mounting during one full extension or retraction of said extensible member.

18. Mounting means for a double-acting hydraulic jack wherein a cylinder carriesa piston for reciprocation therein and a piston rod extends outwardly from the first end of said jack comprising a pivotal mounting on the outer end of said rod, an extension on said cylinder extending outwardly from said firstend, a pivotal mounting positioned on said extension as the sole mounting for said cylinder, said cylinder pivotal mounting being outwardly beyond the retracted position of said rod mounting and in line with the path of said rod mounting on outward movement thereof.

References Cited in the file of this patent UNITED STATES PATENTS 2,704,221 G-winn Mar. 15, 1955 2,841,299 Gildner July 1, 1958 

